Biodegradable polymers have been widely investigated for use, e.g., for human body repair and reconstruction, e.g., for surgical sutures and internal bone fixation, for burn wound coverings, and for drug delivery systems.
Recently, investigations have addressed the possibility of providing reactive sites in biodegradable polymers for bonding to biologically active materials, e.g., for bonding to peptides for use in the tissue engineering or for bonding to drugs for delivery to the body.
Barrera, D. A., Macromolecules, 28, 425-432 (1995) describes poly (lactic-co-lysine) where the side-chain amino groups on the lysine residues are reactive to join to cell-adhesion promoting peptide.
Swindler W. S. U.S. Pat. No. 5,219,980 describes a biodegradable polyester with amine containing functional group as a pendant active site, prepared by synthesis of an unsaturated polyester by polycondensation reaction of maleic anhydride with poyol and then reacting the double bonds of the intermediate polymer with an amine by the well-known Michael reaction.
In neither case is the polymer product derived from a starting material biodegradable polymer which is essentially left intact. Furthermore, the pendant side chains are spaced relatively far apart so a high concentration of reactive sites is not possible.
Barrera, et al., cited above, notes that polylactic acid is a versatile, well-characterized material and is one of the few biodegradable materials used clinically but notes that there are no sites available on this material to modify its surface with biologically active moieties.